Pressure hood with removable seal assembly

ABSTRACT

A pressure hood with a pressure hood body to be used in conjunction with especially a heated cylinder in a machine for the production and/or conversion of a fibrous web, especially a paper-, cardboard- or tissue web, and a seal assembly to seal said pressure hood body against the cylinder, provides that the seal assembly can be inserted into or removed from the pressure hood body—particularly when the pressure hood is installed on the cylinder—through a movement in axial direction relative to the pressure hood body.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of PCT application No. PCT/EP2007/058527,entitled “PRESSURE HOOD HAVING A REMOVABLE SEALING APPARATUS”, filedAug. 16, 2007, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a pressure hood with a pressure hood body to beused in conjunction with especially a heated cylinder in a machine forthe production and/or conversion of a fibrous web, especially a paper-,cardboard- or tissue web, and a seal assembly to seal said pressure hoodbody against the cylinder.

2. Description of the Related Art

A pressure hood of this type is essentially known and is used forexample in a dryer for the continuous drying of a fibrous web coming offthe outer circumference of a heated cylinder. Due to the heat releasedfrom the cylinder to the fibrous web, moisture evaporates from thefibrous web and is absorbed by at least one wire or fabric which travelstogether with the fibrous web and which lays on the fibrous web on theside of said web facing away from the cylinder.

A belt, i.e. a steel belt, follows on the side of the wire or fabricfacing away from the fibrous web against which a pressure medium whichis located inside the pressure hood exerts pressure. In order to sealthe pressure hood against the cylinder—in other words, in order to avoidthe pressure medium escaping from the interior of the pressure hood—aseal assembly is provided. This is equipped with seals progressing inlateral direction, in other words in the circumferential direction ofthe cylinder and transversely to the direction of web travel, in otherwords parallel to the cylinder axis, and which are movable in radialdirection and are pressed against the moisture impermeable belt.

The seals drag on the moisture impermeable belt and are subject toespecially high wear and tear because of the sliding friction thatexists between the seals and the moisture impermeable belt.Consequently, the seals have to be renewed or, respectively replacedoften. Traditionally the entire pressure hood must be removed from thecylinder for this purpose, or the seal assembly must be constructed sothat it can be disassembled and must be taken apart which, respectivelycauses considerable assembly work directly at the machine. This is notonly expensive, but also time consuming, so that expensive down timesare caused by the seal replacement.

What is needed in the art is a pressure hood which permits a simpler andfaster replacement of the seals.

SUMMARY OF THE INVENTION

The present invention provides a pressure hood with a pressure hood bodyto be used in conjunction with especially a heated cylinder in a machinefor the production and/or conversion of a fibrous web, especially apaper-, cardboard- or tissue web, and a seal assembly to seal saidpressure hood body against the cylinder, wherein the seal assembly canbe inserted into or removed from the pressure hood body through amovement in axial direction relative to the pressure hood body, which islocated in particular on the cylinder.

In this context the term “in axial direction” is to be understood to bealways parallel to the rotational axis of the cylinder, whereas a“radial direction” always progresses at right angles to the rotationalaxis of the cylinder. The term “in circumferential direction” refers inthis context to the circumference of the cylinder.

The invention is based on the general concept that the seals, forexample sealing strips, are not mounted individually on the pressurehood, but are instead collectively assembled in a seal assembly whichcan be slid into or out of the pressure hood as an entirety for thepurpose of replacing or exchanging the seals, without having to removethe pressure hood from the cylinder for this purpose.

Once the seal assembly has been slid from the pressure hood theindividual seals are easily accessible and can be exchanged easily andquickly. This shortens the machine down time associated with a sealreplacement or exchange, resulting in a more economical operation of themachine including the cylinder and the pressure hood.

The machine down time can still be further reduced if two sealassemblies are available, whereby a first seal assembly is inserted inthe machine and a second seal assembly with perfect seals is held inreserve. This allows the first seal assembly to be removed from thepressure hood when the seals in the first seal assembly are worn, and toimmediately insert the second seal assembly containing the perfect sealsinto the pressure hood. This reduces machine down times simply to theamount of time which is required to remove and to insert a seal assemblyinto the pressure hood. While the machine operates with the second sealassembly, the worn seals in the first assembly can be removed andreplaced without any time pressure.

According to one design variation the seal assembly includes a sealsupport which is movable in axial direction relative to the pressurehood. The seal support supports the actual seals, which are in theembodiment for example of sealing strips.

The seal support may include two curved sections extending incircumferential direction, which are connected with each other,especially in the area of their ends, through an axial segment extendingin axial direction. In other words the seal support is in the embodimentof a rectangular frame which is curved to follow the shell surface ofthe cylinder or the inside of the pressure hood respectively.

In an effort to improve the rigidity, especially the torsional rigiditythe curved segments can additionally be connected with each otherthrough at least one brace-type reinforcing element.

In order to achieve reliable control of the seal support over its entiretravel path the seal support can—in the area of its axial segments—beguided along the pressure hood body.

According to an additional design variation spacer devices are providedin order to keep the seal assembly during its movement relative to thepressure hood body at least partially at a distance. On the one handthis reduces the friction between the seal support and the inside of thepressure hood body which occurs during the movement of the sealassembly, thereby reducing the force necessary for moving the sealassembly. On the other hand it prevents that a seal, for example asealing ring located between the seal support and the inside of thepressure hood body is damaged.

Forces or movements respectively can be exerted through the spacerdevices in radial direction and/or in tangential direction upon the sealassembly. Through a suitable combination of radial and tangential forcesor tangential movements the large surface of the seal assembly can bekept at a distance from the inside of the pressure hood body.

In addition the spacer devices can be located in an area of axialsegments of a seal support of the seal assembly. Through an appropriateapplication of radial and tangential forces or movements upon the axialsegments, the seal support can be compressed radially, and also at thesame time be activated in circumferential direction, so that the curvedsections of the seal support can be held at a distance, essentially overtheir entire length to the inside of the pressure hood body.

According to one design variation the spacer devices can include atleast one guide extending in axial direction and at least one roll- orglide element which is guided by the guide, whereby the guide iscontoured to cause a movement in certain places in radial direction ofthe roll or glide element. Due to the contour in the guide a radialforce or respectively movement can be exerted especially easily upon theaxial segments of the seal support through the combined effect of guideand roll- or glide element.

The guide can be mounted on the pressure hood body and the roll- orglide element can be installed on the seal support. Basically however,an opposite arrangement is also feasible where the guide is mounted onthe seal support and the roll- or glide element is installed on thepressure hood body.

According to an additional design variation at least one guide isequipped in addition with one contour, especially grooves withdescending and/or ascending ramps causing the roll or glide element incertain places to move in circumferential direction. The contour basedmovement of the roll or glide element in circumferential directionrepresents a simple method of exerting a tangential force orrespectively movement upon the seal support and contributes to holdingthe seal assembly at a distance to the inside of the pressure hood body.

Alternatively, or in addition to a contour of this type at least oneguide can be mounted on the pressure hood body, movably incircumferential direction relative to the pressure hood body. A guide ofthis type for example can be moved by way of a pneumatically orhydraulically inflatable pressure tube or also manually incircumferential direction.

According to an additional design variation especially a single- ormultistage seal is provided all around on one side of the sealingassembly facing away from the pressure hood body. The seal seals theinterior of the pressure hood vis-à-vis the cylinder, or respectivelyvis-à-vis a moisture impermeable belt which is routed around thecylinder. Especially a multistage seal can effectively prevent leakagefrom the pressure hood of a medium which is pressurized inside thepressure hood.

The seal can include a sealing strip and especially several sealingstrips located parallel to each other. Each of the parallel positionedsealing strips represents a sealing stage of a multistage seal. Thesealing strip or each sealing strip can be placed in a groove that isprovided in a seal support of the seal assembly.

According to an additional design variation the pressure of the sealingstrip or of each sealing strip acting against the cylinder isadjustable. This permits a desired sealing result to be adjusted and tobe maintained when the sealing strips begin to wear.

For example a pressure tube can be provided to adjust the pressureexerted by the sealing strips. By supplying the pressure tube with asuitable pressure fluid, for example compressed air, compressed water,compressed oil, etc., the pressure tube can be inflated in order toactivate the associated sealing strips for the purpose of adjusting thedesired pressure force.

The pressure tubes can in particular—always with associated sealingstrips—be supplied independent from each other. According to anadditional design variation each pressure tube forms in particular aclosed ring. This can be produced for example by flush gluing togetherof the tube ends.

The pressure tube can have a bellows-type cross section, at least insections. In addition, two opposite side walls of the pressure tube canbe connected with each other by at least one cross link, whereby in across sectional view at least two pressure tube chambers are formed.This pressure tube geometry ensures an especially large stroke and atthe same time especially smooth running during expansion of the pressuretube, thereby on the one hand enabling increased permissible wear andtear—that is in other words a longer service life of the seal—and on theother hand a more sensitive response to a change in the pressure force.

According to an additional design variation a first canal for theremoval of pressure medium from a space that is defined by a first and asecond sealing strip—viewed from the interior of the pressure hoodtoward the outside—is provided. Through this canal pressure medium whichhas escaped past the first sealing strip from the inside of the pressurehood can be removed The removed pressure medium can be collected and/orreturned via an appropriate line into a storage tank or respectivelyagain into the inside of the pressure hood.

In addition a second canal for the removal of pressure medium from aspace that is defined by a second and third sealing strip—viewed fromthe interior of the pressure hood toward the outside—can be provided.With the sealing assembly completely inserted into the pressure hoodbody the second canal can be connected, for example with a suctiondevice, thereby preventing the leakage of pressure medium from thepressure hood even more effectively.

According to an additional design variation the sealing strip or eachsealing strip is composed of several sealing strip segments which aremovable relative to each other at their joint. Adjoining sealing stripsegments may have extensions on their ends facing each other whichengage tongue and groove fashion with each other.

Due to the movability of the sealing strip segments a length adjustmentis created, which is necessary especially when the sealing strips whichextend in circumferential direction have to be adjusted to a changingradius because of wear and tear. A length adjustment is alsoadvantageous on the sealing strips which extend in axial direction,since the sealing strips and the seal support typically have differentheat expansion coefficients and therefore experience different lengthchanges if they absorb different temperatures during machine operation.Lastly, the length adjustment prevents distortions of the sealing stripsin the seal support and ensures smooth running of the seal, that is ofthe contact pressure of the sealing strips in radial direction.

In order to avoid damage during pressure contact to the pressure tubewhich could result due to a reduced contact surface at the jointlocations, the joint location could be provided with a cover at the sideof the pressure tube. For example they could be covered by thin plates.

According to an additional design variation ways are provided to preventespecially a sealing strip segment which is located in a curved segmentof the seal support from moving in longitudinal direction of the sealingstrip segment, relative to the seal support. In this way correctpositioning of the sealing strip segments, especially of the sealingstrip segments extending in circumferential direction, is permanentlyensured.

The ways may for example include a pin-type element extendingtransversely through the sealing strip segment which is secured on theseal support to prevent a movement in longitudinal direction of thesealing strip segment. The pin-type element may be movable in radialdirection relative to the seal support, so that the desired contactpressure can also always be adjusted with a sealing strip which extendsin circumferential direction. The pin-type element may be in theembodiment of for example a bolt, a pin or a screw.

According to an additional design variation a seal is provided allaround on a side of the seal assembly facing the pressure hood body.This ensures that the seal assembly when inserted into the pressure hoodbody is sealed vis-à-vis the pressure hood body. The seal may forexample include especially a closed seal ring, for example in form of anO-ring, packing or a pneumatic tube.

An additional subject of the invention is also an arrangement includinga pressure hood of the type previously described and at least onechange-over rack to accommodate a seal assembly that was removed fromthe pressure hood body or one that is to be inserted into the pressurehood body. The change-over assembly serves to support the seal assemblyin its removed state and contributes to a simpler and faster exchange ofthe worn seals.

The change-over rack can be designed such and can be located relative tothe pressure hood such that the seal assembly can be accommodated by thechange-over rack simultaneously with its removal from the pressure hoodbody. In this way the change-over rack can be positioned at the pressurehood body so that the seal assembly, when it is slid from the pressurehood body, is immediately slid into the change-over rack and that afterchecking or respectively replacement of the seal in the change-over rackis again slid into the pressure hood body. During the process of slidingthe seal assembly in and/or out, the change-over rack can be connectedwith the pressure hood body, especially through screws and/or clamps.

In order to reduce the machine down time even further and to simplifythe replacement of seals even further, two change-over racks may beprovided, whereby the one change-over rack is provided to receive afirst seal assembly that is to be removed from the pressure hood body,and the other change-over rack carries a second seal assembly to beinserted into the pressure hood body in place of the first sealassembly. Immediately after sliding the first seal assembly from thepressure hood body, the second seal assembly can therefore be insertedinto the pressure hood body and machine operation can be resumed. Whilethe machine operation is continued with the second seal assembly, theworn seals from the first seal assembly can be renewed or replaced,thereby preparing the first seal assembly for renewed service in thepressure hood.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is an inventive pressure hood mounted on a cylinder, with apressure hood body and seal assembly which is partially slid out of thepressure hood body and a change-over rack to accommodate the sealassembly that is removed from the pressure hood body;

FIG. 2 is a seal support of the seal assembly in FIG. 1;

FIG. 3 is a cross section through a section of the seal assemblydepicted in FIG. 1 that is inserted in the pressure hood body;

FIG. 4 is a connecting joint of two sealing strip segments of the sealassembly depicted in FIG. 1, extending in circumferential direction;

FIG. 5 is a bolt extending transversely through a sealing strip whichprogresses in circumferential direction, in order to prevent movement ofthe sealing strip in circumferential direction;

FIG. 6 is a schematic cross sectional view of the seal assembly depictedin FIG. 1 which is inserted in the pressure hood body;

FIG. 7 is a cross sectional view of a first axial segment of the sealsupport depicted in FIG. 2, inserted in the pressure hood body;

FIG. 8 is an alternative design variation of a pressure hood body guidefor the first axial segment of the seal support in FIG. 2; and

FIG. 9 is a cross sectional view of a second axial segment of the sealsupport in FIG. 2, inserted in the pressure hood.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate embodiments of the invention, and such exemplifications arenot to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIG. 1, there isshown a heated cylinder, as used in paper production for example forcontinuous drying of a fibrous web which is not illustrated here, forexample a paper, cardboard or tissue web and which for this purpose runsat least partially over the circumferential surface of the cylinder.

A pressure hood 11 with a pressure hood body 12 is mounted on thecylinder. Viewed in axial direction the pressure hood body envelopes thecircumferential surface of the cylinder 10 essentially over the entirewidth and viewed in circumferential direction to approximately threequarters of the cylinder circumference. The interior of the pressurehood 11 can be filled with a pressure medium, for example with waterwhich can have an overpressure of several bar relative to thesurroundings in order to press against the cylinder 10 a moistureimpermeable belt 13 (FIG. 3) which runs between the pressure hood 11 andthe fibrous web that is to be dried and, together with the fibrous web,runs over the cylinder 10.

In order to seal the pressure hood 11 against the moisture impermeablebelt 13, a seal assembly 14 is provided which is movable in axialdirection relative to the pressure hood body 12. With the pressure hoodbody 12 mounted on the cylinder 10 the seal assembly 14 can be slid inand out of the pressure hood body 12 in a gap formed between thepressure hood body 12 and the cylinder 10, in order to exchange orreplace worn seals.

A change-over rack 16 is provided for the retention of the seal assembly14 after its removal from the pressure hood body 12. It is designed thatit can be positioned relative to the pressure hood 11 so that the sealassembly 14 glides directly from the pressure hood body 12 into thechange-over rack.

In order to keep the down time of the machine which includes thecylinder 10 and the pressure hood 11 as short as possible during areplacement of the seals, two same-type change-over racks 16 and sealassemblies 14 may be utilized, whereby always one functional sealassembly 14 is inserted into the pressure hood body 12, and at the sametime always the other seal assembly 14, after replacement of its seals,is held in reserve for an exchange with the one seal assembly 14.

As illustrated in FIG. 2, the seal assembly 14 includes a frame-typeseal support 18. This includes two curved segments 20 which extend incircumferential direction of the cylinder 10 and whose radius ofcurvature is selected to be somewhat greater than the outside radius ofthe cylinder 10. The curved segments 20 are connected with each other ateach of their ends through an axial segment 22 which extends in axialdirection that is parallel to the cylinder axis. To increase therigidity of the seal support 18 one, two or more brace-type stiffeningelements 24 are provided which connect the curved segments 20 with eachother in areas between the axial segments 22.

On one outside 26 of the seal support 18 facing toward the pressure hoodbody 12, a closed sealing ring 28, for example a O-ring, packing, apneumatic tube or similar device is inserted into a correspondinglycontinuous groove 30 (FIG. 3) in order to seal the seal support 18relative to the pressure hood body 12. In place of only one sealing ring28, a plurality of such sealing rings may be provided. The seal support18 is screw fastened with the pressure hood 12 by way of a screw 31which is schematically indicated in FIG. 3.

As can be seen in FIGS. 2 and 3 three continuous grooves 34 are providedon an inside 32 of the seal support 18 facing the cylinder 10 whichextend parallel to each other along the curved segments 20 and the axialsegments 22. Sealing strips 36, 38, 40 are inserted into the grooves 34which serve to seal the seal support 18 against the moisture impermeablebelt 13. In contrast to FIG. 3, only two sealing strips are depicted inFIG. 2.

The sealing strips 36, 38, 40 are inserted into the grooves 34 in such away that they can be pressed against the moisture impermeable belt 13through a movement in radial direction.

For the purpose of pressing the sealing strips 36, 38, 40 against thebelt 12, pressure tubes 42 are provided which are inserted in thegrooves 34 and which exhibit a bellows-like cross section and which canbe expanded through applying a suitable pressure fluid, for examplecompressed air, compressed water, compressed oil, etc. in order to seatthe sealing strips 36, 38, 40 in radial direction.

The sealing strips 36, 38, 40 are stationary relative to the moistureimpermeable belt 13 running over the cylinder 10. They are thereforedragging seals. With this type of seal it cannot be avoided thatpressure medium can escape from the interior of the pressure hood 11—theso-called pressure chamber 44. Moreover, the first sealing strip 36—whenviewed from the interior of the pressure hood 11 toward theoutside—causes a pressure drop, so that the pressure medium collectingin the first gap 46 between the first sealing strip 36 and the secondsealing strip 38 has a reduced pressure, perhaps only half as high,compared to the pressure medium in pressure chamber 44.

A discharge canal 48 is provided in the seal support 18 for the purposeof removing the escaped pressure medium from the first gap 46. Thedischarged medium can be collected and respectively led back into thepressure chamber 44. In order to increase the volume of the first gap46, an additional groove 50 is built into the seal support 18.

In order to even more effectively prevent leakage of pressure mediumfrom the pressure hood 11 a third sealing strip 40 is provided inaddition to the first and the second sealing strips 36, 38, therebyproviding a total of a three-stage seal. Basically it is however alsopossible to provide a seal with a number of sealing strips that differsfrom the three aforementioned.

The second sealing strip 38 and the third sealing strip 40 define asecond gap 52. The second gap 52 is connected with a second dischargecanal 54 in the seal support 18 which, when installed in the pressurehood body 12 of the seal assembly 14 can be connected with a suctiondevice with which the pressure medium that collects in the second gap 52can be sucked away.

The sealing strips 36, 38, 40 are always composed of several sealingstrip segments which are movable relative to each other at theirconnecting locations. FIG. 4 illustrates such a connecting location oftwo sealing strip segments 56 on a sealing strip which is inserted in acurved segment 20 of the seal support 18. As can be seen in FIG. 4, thesealing strip segments 56 have offset tab-type extensions 58 on theirends facing each other which engage in tongue and groove fashion witheach other.

Due to the movability of the sealing strip segments 56 relative to eachother a length adjustment is created, which is necessary especially whenthe sealing strips which progress in circumferential direction have tobe adjusted to a changing radius because of wear and tear. A lengthadjustment is however also advantageous on the sealing strip segments 56extending in axial direction, since the sealing strips 36, 38, 40 andthe seal support 18 have different length expansion coefficients due todifferent materials and therefore can experience different lengthchanges if they absorb different temperatures during machine operation.Lastly, the hereby created length adjustment prevents distortions of thesealing strips 36, 38, 40 in the seal support 18 and ensures smoothcontact pressure of the sealing strips 36, 38, 40 in radial direction.

In order to avoid damage of the pressure tube 42 which is allocated to asealing strip 36, 38, 40 which could result due to a reduced contactsurface at the joint locations between the individual sealing stripsegments 56, thin cover plates 60 are arranged in the area of the jointlocation, between the sealing strip segments 56 and the associatedpressure tube 42.

In order to prevent the individual segments 56 of the sealing strips 36,38, 40 which are inserted into the curved segments 20 of the sealsupport 18 from shifting in circumferential direction, said sealingstrip segments 56 are secured by a bolt 62 extending transverselythrough them and which is located movably in a recess 64 of the curvedsegment 20, extending in radial direction. In order to achieve optimummovability of the bolt 62 inside the recess 64, the bolt 62 is alwayspositioned in a sliding block 66 that is inserted in the recess 64.Basically however, the bolt can also be used feasibly without slidingcomponents. The sealing strip segments 56 can always be twisted aroundtheir bolt 62.

The glide component 66 serves essentially to enlarge the contact surfacein the recess 64 and does not necessarily have to be an individualcomponent, but can also be represented by the bolt 62 itself, forexample through a flattened two-edged or square head.

According to an additional design variation the bolt 62 may be in theform of a special screw with a square head on the one side (glidecomponent 1), a locating/sealing surface in the area of the sealingstrip segment 56 and an outside thread on the other side on which asquare nut (sliding component 2) is located. Passage of the pressurewater through the sealing strip segment 56 via the locating/sealingsurface can be impeded by additional ways, for example an O-ring seal.

Because of the movability of the bolts 62 in the recesses 64 whichextend in radial direction, a reliable contact pressure of the sealingstrip segments 56 in radial direction upon the cylinder 10 is ensured,even when the seals begin to wear.

FIGS. 7 and 8 show that in the end areas located in the circumferentialdirection 68, 70 of the pressure hood body 12 (FIG. 6) a guide 72, 74respectively is provided which extend in axial direction and on whichthe seal assembly 14 is guided by way of a roll 78, which is connectedvia a mounting bracket 76 with the seal support 18. Each guide 72, 74has an upward facing edge area 80 on which the respective roll 78, whichfor this purpose features a V-shaped profile, runs.

It is however also conceivable to have a roll with an outward facingV-shaped profile run in an inside edge, for example in a notch or slot.In principle, rolls having a cylindrical, conical or ball-shape arefeasible. In addition the support may occur through several rolls,located in different—preferably vertical relative to eachother—directions.

FIGS. 7 and 9 illustrate the sealing assembly 14 in each instance in acompletely inserted position in the pressure hood body 12, whereby theseal support 18 is in contact with the inside 32 of the pressure hoodbody 12 with its outside 26.

In order to create an impermeable as possible connection in thissituation between the seal assembly 14 and the pressure hood body 12with regard to the pressure medium on the inside of the pressure hood11, the seal support 18 can be mounted on the pressure hood body 12 byway of a screw connection and/or a clamp connection.

FIG. 7 illustrates a variation of a screw connection whereby an axialsegment 22 of the seal support 18 is screwed together by way of a screw(not illustrated) with the pressure hood body 12. The screw would belocated in a bore 82 in the pressure hood body 12 and engage in athreaded bore 84 in the axial segment 22.

FIG. 9 illustrates a clamp connection variation, whereby a firstL-shaped profiled strip 86 is screwed onto the outside 26 of an axialsegment 22 by way of a screw (not illustrated) which is located in abore 88. The first L-shaped profiled strip 86 engages at the back of asecond L-shaped profiled strip 90 which is contained on the pressurehood body 12 by way of a sleeve 92 which extends through a bore in thepressure hood 12 and a screw (not illustrated) which is fixed on anopposing support 94.

On opposite sides of this screw, grooves 96 are provided in the opposingsupport 94 in which pressure tubes 98 that are supplied with pressurefluid are located. The grooves 96 are enclosed by support strips 100which support themselves on the outside of the pressure hood 12 andwhich extend at least partially into the grooves 96.

In order to secure the seal assembly 14 onto the pressure hood body 12the pressure tubes 98 are supplied with pressure fluid, thereby causingthe pressure tubes 98 to expand. Due to their expansion the pressuretubes 98 which support themselves on the support strips 100 seat againstthe opposing support 94 in radial direction toward the outside, therebypulling the second profiled strip 90 toward the outside over the screwwhich is not illustrated. This movement of the second L-shaped profiledstrip 90 causes also the axial segment 22 of the seal support 18 to bepulled toward the outside over the first L-shaped profile strip 86,thereby pressing it against the pressure hood body 12.

The first L-shaped profile strip 86 and the second L-shaped profilestrip 90 are located in a groove 102 of the pressure hood body 12 whichextends in axial direction and whose cross section is selected such thatthe profile strips 86, 90 have sufficient clearance to pull the sealsupport 18 to the pressure hood body 12, however have practically noclearance viewed in circumferential direction in order to prevent amovement of the axial segment 22 in circumferential direction relativeto the pressure hood body 12 through which the profile strips 86, 90 candisengage.

Securing of the seal support 18 by way of the clamp connection on thepressure hood body 12 has the advantage that no screws have to beactuated. The clamp connection is therefore especially suitable for usein areas that have poor access.

When sliding the seal assembly 14 into the pressure hood 11 orrespectively when sliding the seal assembly 14 out of the pressure hood11 it is advantageous if there is a radial distance between the sealsupport 18 and the pressure hood body 12, in order to keep friction lowon the one hand, and as not to damage the static sealing ring on theother hand.

In order to create such a radial distance between the sealing assembly14 and the pressure hood body 12, the seal support 18 is deformed to asmaller radius through forces or respectively movements which areeffective in radial and tangential direction, as indicated in FIG. 6 bythe arrows 104, 106.

In order to generate these forces, or respectively movements, a contouris provided in the upper edge area 80 of the guide 72 illustrated inFIG. 7 which ensures that the roll 78 is offset in circumferentialdirection as well as in radial direction away from the pressure hoodbody 12—in FIG. 7 to the left and upward—as soon as the roll 78 leavesits final position shown in FIG. 7 and in which the seal assembly 14 iscompletely inserted in the pressure hood body 12. This offset of theroll 78 causes a radial force or respectively movement 104 radiallytoward the inside, and also a tangential force or respectively movement106 in circumferential direction through which the seal assembly 14 isheld at a distance from the pressure hood body.

FIG. 8 illustrates an alternative variation of the guide 72 which doesnot possess a contour for the excursion of the roll 78 incircumferential direction. Instead it is positioned movably inapproximately tangential direction at the pressure hood body 12. Toactivate the seal support 18 with a tangential force 106, the guide 72is moved accordingly by way of a pressure tube 108 that can be suppliedwith a suitable pressure fluid.

Similar to the guide 72 in FIG. 7, guide 74 in FIG. 9 is also equippedwith a contour for the excursion of the roll 78. However, the contour ofthe guide 74 is designed so that the roll 78 is offset only in radialdirection toward the inside when it leaves its end position when theseal assembly 14 is slid from the pressure hood 11. Exerting atangential force or respectively movement in circumferential directionupon the seal support 18 is not provided for in the clamp connectionvariation illustrated in FIG. 9 since—as already mentioned—a movement ofthe axial segment 22 in circumferential direction relative to thepressure hood body 12 is only limited or respectively impossible becauseof the L-shaped profile strips 86, 90 which are located in the groove102 of the pressure hood 12.

In order to produce a distance between the seal assembly 14 and thepressure hood 12, in other words in the area of both axial segments 22of the seal support 18, an inward directed radial force or respectivelymovement 104 is exerted upon the seal support 18 (FIG. 6) in the heredescribed design variation. However, a tangential force or respectivelymovement 106 is exerted upon the seal support 18 only in the area of oneof the two axial segments 22. The reason for this asymmetric exertion ofthe tangential force or respectively movement 106 is based in theattachment of the one axial segment 22 on the pressure hood 12 by way ofa clamp connection (FIG. 8) which, as already mentioned, allows no oronly a limited movement of the axial section 22 relative to the pressurehood in circumferential direction. In principle it is however alsoconceivable to attach both axial segments 22 to the pressure hood 12 byway of a screw connection so that tangential forces or respectivelymovements 106 can be exerted at both axial segments 22 upon the sealsupport 18.

COMPONENT IDENTIFICATION LISTING

-   10 Cylinder-   11 Pressure Hood-   12 Pressure hood body-   13 Moisture impermeable belt-   14 Seal assembly-   16 Change-over rack-   18 Seal support-   20 Curved segment-   22 Axial segment-   24 Stiffening element-   26 Outside-   28 Sealing ring-   30 Groove-   31 Screw-   32 Inside-   34 Groove-   36 Sealing strip-   38 Sealing strip-   40 Sealing strip-   42 Pressure tube-   44 Pressure chamber-   46 Gap-   48 Discharge canal-   50 Groove-   52 Gap-   54 Discharge canal-   56 Sealing strip segment-   58 Extension-   60 Cover plates-   62 Bolt-   64 Recess-   66 Sliding block-   68 End area-   70 End area-   72 Guide-   74 Guide-   76 Mounting bracket-   78 Roll-   80 Edge area-   82 Bore-   84 Threaded bore-   86 L-shaped profile strip-   88 Bore-   90 L-shaped profile strip-   92 Sleeve-   94 Opposing support-   96 Groove-   98 Pressure tube-   100 Support strip-   102 Groove-   104 Radial force or respectively, movement-   106 Tangential force or respectively, movement-   108 Pressure tube

While this invention has been described with respect to at least oneembodiment, the present invention can be further modified within thespirit and scope of this disclosure. This application is thereforeintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

1. A pressure hood to be used in conjunction with a heated cylinder in amachine for at least one of a production and a conversion of a web offibrous material, said pressure hood comprising: a pressure hood body; aseal assembly configured for sealing said pressure hood body against theheated cylinder, said seal assembly configured for being one of insertedinto and removed from said pressure hood body through a movement in anaxial direction relative to said pressure hood body.
 2. The pressurehood according to claim 1, wherein said seal assembly is configured forbeing one of inserted into and removed from said pressure hood body,when said pressure hood is installed on the cylinder, through saidmovement in said axial direction relative to said pressure hood body. 3.The pressure hood according to claim 1, wherein said seal assemblyincludes a frame-type seal support which is movable in said axialdirection relative to said pressure hood body.
 4. The pressure hoodaccording to claim 3, wherein said seal support includes at least oneaxial segment extending in said axial direction and two curved segmentsextending in a circumferential direction, said curved segments beingconnected with each other through said at least one axial segmentextending in said axial direction.
 5. The pressure hood according toclaim 4, wherein said curved segments include a plurality of end areas,said curved segments being connected with each other in said pluralityof end areas through said axial segment extending in said axialdirection.
 6. The pressure hood according to claim 4, wherein said sealsupport includes at least one stiffening element, said curved segmentsbeing in addition connected with each other by at least one saidstiffening element.
 7. The pressure hood according to claim 4, whereinsaid at least one axial segment includes a plurality of said axialsegments, said seal support being guided in an area of said plurality ofaxial segments on said pressure hood body.
 8. The pressure hoodaccording to claim 7, wherein when said seal assembly is fully insertedinto said pressure hood body said seal assembly is configured for beingsecured on said pressure hood body by way of at least one of a screwconnection and a clamp connection.
 9. The pressure hood according toclaim 7, wherein when said seal assembly is fully inserted into saidpressure hood body said seal assembly is configured for being secured onsaid pressure hood body by way of at least one of a screw connection anda clamp connection in an area of said plurality of axial segments ofsaid seal support.
 10. The pressure hood according to claim 7, furthercomprising a plurality of guides, wherein, during movement of said sealassembly relative to said pressure hood body, said seal assembly isguided by said plurality of guides located in said area of saidplurality of axial segments of said seal support at said pressure hoodbody and extending in said axial direction.
 11. The pressure hoodaccording to claim 10, further comprising a plurality of spacer devices,said plurality of spacer devices configured for keeping said sealassembly during movement of said seal assembly relative to said pressurehood body at least partially at a distance from an inside of saidpressure hood body.
 12. The pressure hood according to claim 11, whereinsaid plurality of spacer devices are configured for being that throughwhich one of a plurality of forces and respectively a plurality ofmovements can be exerted in at least one of a radial direction and acircumferential direction upon said seal assembly.
 13. The pressure hoodaccording to claim 11, wherein said plurality of spacer devices arelocated in said area of said plurality of axial segments of said sealsupport of said seal assembly.
 14. The pressure hood according to claim11, wherein said plurality of spacer devices includes at least one saidguide extending in said axial direction and at least one roll or glideelement which is guided by said at least one guide, said at least oneguide including a contour which, in certain places, causes a movement ofsaid roll or said glide element in a radial direction.
 15. The pressurehood according to claim 11, wherein said plurality of spacer devicesincludes at least one said guide extending in said axial direction andat least one roll or glide element which is guided by said guide, saidat least one guide including a contour which, in certain places, causesa movement of said roll or said glide element in said circumferentialdirection.
 16. The pressure hood according to claim 15, wherein saidplurality of guides includes a first guide which is mounted at saidpressure hood body and is movable in said circumferential directionrelative to said pressure hood body.
 17. The pressure hood according toclaim 7, wherein said seal assembly includes a seal which is providedall around on one side of said seal assembly that is facing away fromsaid pressure hood body.
 18. The pressure hood according to claim 17,wherein said seal is one of a single and a multi-stage seal.
 19. Thepressure hood according to claim 17, wherein said seal includes one of asealing strip and a plurality of sealing strips progressing parallel toeach other.
 20. The pressure hood according to claim 19, wherein saidone of said sealing strip and said plurality of sealing strips is placedin respectively one of a groove and a plurality of grooves in said sealsupport of said seal assembly.
 21. The pressure hood according to claim20, wherein a force of a pressure of said one of said sealing strip andsaid plurality of sealing strips on the cylinder is adjustable.
 22. Thepressure hood according to claim 21, wherein said force of said pressureof said plurality of sealing strips on the cylinder is adjustableindependent of each other.
 23. The pressure hood according to claim 21,wherein said sealing assembly includes a pressure tube configured foradjusting a contact pressure of said plurality of sealing strips. 24.The pressure hood according to claim 23, wherein said pressure tube is aclosed endless ring.
 25. The pressure hood according to claim 24,wherein said pressure tube possesses a bellows-type cross section. 26.The pressure hood according to claim 23, wherein a cross sectional viewof said pressure tube shows at least two chambers which are connected byat least one cross link extending between two side walls of saidpressure tube that are located opposite each other.
 27. The pressurehood according to claim 23, wherein said plurality of sealing stripsincludes a first sealing strip and a second sealing strip, said sealingassembly including a first canal configured for removing a pressuremedium from a space that is defined by said first sealing strip and saidsecond sealing strip viewed from an interior of the pressure hood towardan outside of the pressure hood.
 28. The pressure hood according toclaim 27, wherein said plurality of sealing strips includes a thirdsealing strip, said sealing assembly including a second canal configuredfor removing said pressure medium from a space that is defined by saidsecond sealing strip and said third sealing strip viewed from saidinterior of the pressure hood toward said outside of the pressure hood.29. The pressure hood according to claim 28, wherein, at least with saidsealing assembly completely inserted in said pressure hood body, saidsecond canal is configured for being connected with a suction device.30. The pressure hood according to claim 23, wherein one of said sealingstrip and each of said plurality of sealing strips is composed of aplurality of sealing strip segments which are movable relative to eachother at a plurality of connecting locations of said plurality ofsealing strip segments.
 31. The pressure hood according to claim 30,wherein said plurality of connecting locations are equipped with a coveron a side of said pressure tube.
 32. The pressure hood according toclaim 30, wherein adjoining ones of said plurality of sealing stripsegments include ends facing each other having extensions which engagein tongue-and-groove fashion with each other.
 33. The pressure hoodaccording to claim 30, further comprising a device configured forpreventing one said sealing strip segment which is located in one saidcurved segment of said seal support from moving in a longitudinaldirection of said one sealing strip segment relative to said sealsupport.
 34. The pressure hood according to claim 33, wherein saiddevice includes a pin-type element extending transversely through saidone sealing strip segment which is secured on said seal support toprevent movement in said longitudinal direction of said one sealingstrip segment and is movable in a radial direction relative to said sealsupport.
 35. The pressure hood according to claim 34, further comprisinga guide block, wherein said pin-type element is moved, in an area of atleast one end of said pin-type element, on said seal support by way ofsaid glide block.
 36. The pressure hood according to claim 34, whereinsaid one sealing strip segment can turn around an axis of said pin-typeelement relative to said seal support.
 37. The pressure hood accordingto claim 36, wherein said pin-type element is one of a bolt, a pin, anda screw.
 38. The pressure hood according to claim 1, further comprisinga seal provided all around said seal assembly on a side facing saidpressure hood body.
 39. The pressure hood according to claim 38, whereinsaid seal includes at least one closed seal ring.
 40. An arrangement,comprising: a pressure hood configured for being used in conjunctionwith a heated cylinder in a machine for at least one of a production anda conversion of a web of fibrous material, said pressure hood including:a pressure hood body; a seal assembly configured for sealing saidpressure hood body against said heated cylinder, said seal assemblyconfigured for being one of inserted into and removed from said pressurehood body through a movement in an axial direction relative to saidpressure hood body; and at least one change-over rack configured foraccommodating said seal assembly one of when said seal assembly has beenremoved from said pressure hood body and when said seal assembly is tobe inserted into said pressure hood body.
 41. The arrangement accordingto claim 40, wherein said change-over rack is configured for beingpositioned relative to said pressure hood such that said seal assemblycan be accommodated by said change-over rack simultaneously with aremoval of said seal assembly from said pressure hood body.
 42. Thearrangement according to claim 41, wherein said change-over rack isconfigured for being secured in a mounting position relative to saidpressure hood.
 43. The arrangement according to claim 40, wherein saidat least one change-over rack includes a first said change-over rack anda second said change-over rack, said first change-over rack configuredfor receiving a first said seal assembly that is to be removed from saidpressure hood body, said second change-over rack configured for carryinga second said seal assembly to be inserted into said pressure hood bodyin place of said first seal assembly.